The objective of this proposed project is to alter the intervening sequence of the yeast suppressor tRNATyr by enzymatic methods and by chemical synthesis. The suppressor tRNATyr carrying altered or deleted intervening sequences will be cloned in yeast and tested for in vivo suppressor activity. By correlating the structure and function, we hope to define the size and the sequence of intervening sequences required for recognition by the splicing enzyme which removes it from the precursor RNA molecule.